The invention concerns a thrust chamber of a driving mechanism for satellites and transport devices for space travel uses as well as its position control drive mechanism and especially for transport devices which bring satellites from the flight path of the carrier rockets into the satellite service path.
Drive mechanisms of this type have an injection head through which the propellants, which for example the fuel MMH (hydrazine compound) and an oxidizer N204 (nitrogen tetroxide) are injected into the thrust chamber with a combustion chamber, nozzle element and expansion nozzle installed on the injection head. Very high temperatures arise during combustion of the propellants, in the range up to 2600xc2x0 C. in the core of the thrust chamber, that is, in the combustion gases. The wall of the nozzle element is heated up here to a temperature of approximately 1600xc2x0 C. For this reason, up until now, nozzle elements have largely been used in the walls of which cooling channels are provided which are cooled with propellants which are subsequently fed to combustion. Regeneratively cooled nozzle elements of this sort are nonetheless expensive to manufacture and have disadvantages in operating behavior during the ignition and shutting down of the drive mechanisms.
By using high temperature materials such as platinum-iridium (Ptxe2x80x94Ir) alloys, regenerative cooling construction methods of this type can be dispensed with. A disadvantage in using such high temperature materials is that these cannot be adequately joined with the materials which are used for the combustion chamber adjoining the nozzle element as well as the expansion nozzle, for example, with chromium-nickel-molybdenum alloys, using welding techniques. Owing to differences in physical properties, such as melting point, thermal expansion, specific weight, no sufficient crystalline connection takes place in the crystalline matrix structure of Ptxe2x80x94Ir and chromium-nickel-molybdenum alloys when these two metal alloys are welded. Scanning electron microscope (REM) observations show a marked crystalline boundary layer of a few thousandths of a millimeter thick (xcexc range) in the melting zone in the platinum-iridium alloy. For this reason, it is not possible to speak of a classical melting. The welded connections obtained here for this reason do not have the requisite dynamic stability and lead to breakage under vibration stress.
It is therefore an objective of the invention to create a thrust chamber for satellites and space travel transport devices where the use of regenerative nozzle elements is not necessary and whose walls possess a sufficient stability at temperatures up to 1600xc2x0 C.
This objective is accomplished by providing a thrust chamber housing for a driving mechanism for space travel applications which is fastened with one end on an injection head and which has a combustion chamber housing of a highly heat-resistant steel, a nozzle element of a platinum-iridium alloy and an expansion nozzle housing of a highly heat-resistant steel, characterized in that the combustion chamber housing is welded through a first intermediate ring with the nozzle element, and the nozzle element is welded through a second intermediate ring with the expansion nozzle housing by means of welded connections, whereby the first and the second intermediate ring are made of a platinum-rhodium alloy. Further embodiments are described herein and in the claims.
The thrust chamber of the invention has the advantage that this can be manufactured relatively simply and with low costs. A further advantage is that already existing driving mechanism constructions can basically be retained and the requisite operating stability can be attained with simple modifications.
The invention will be described below on the basis of the appended drawing which shows a thrust chamber of the invention together with an injection head in a perspective, exploded representation.